<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>事件驱动</title>
</head>

<body>
    <div>商品数量 <input id="goodsnum" /></div>
    <div>商品价格 <input id="goodsprice" /></div>
    <div>小计 <span id="total"></span></div>
</body>
<script>
    let goodsnumInput = document.getElementById("goodsnum");
    let goodspriceInput = document.getElementById("goodsprice");
    let  totalSpan = document.getElementById("total");
    goodsnumInput.oninput = function(){//文本框架有内容改变会触发
        totalSpan.innerHTML  = goodsnumInput.value * goodspriceInput.value;
    }
    goodspriceInput.oninput = function(){//文本框架有内容改变会触发
        totalSpan.innerHTML  = goodsnumInput.value * goodspriceInput.value;
    }



</script>

</html>